A:
Playstation plus, is a subscription with sony, similar to xbox gold. It's required to have PlayStation plus in order to access online playing on any ps4. Also, it will give you some PlayStation store discounts, and 2 free games each months. Free games are not the best.
PlayStation network cards, is like PlayStation gift card. It has money inside that can be use on the PlayStation store to buy games, rent movies, avatars, buy in game content or games add ons.